The present invention relates generally to electronic components, and more particularly, to a multilayer radio frequency interconnect system.
Multilayer support structures for electronic components are well known. Examples of known support structures include multiple wiring layer printed circuit boards, multichip modules (MCMs) and high density multichip modules (HDMIs) employing multiple wiring layer substrates, and multiple wiring layer single integrated circuits (ICs). The wiring layers are separated from one another by dielectric materials such as, for example, phenolic resin, epoxy, ceramic, silicon, silicon dioxide or polyimide.
A conventional method for electrically connecting one wiring layer to another, i.e., xe2x80x9cinterlayer connection,xe2x80x9d is by a perpendicular conductive through-via extending from one layer, through the dielectric, to the other layer. The other layer may be, for example, a signal layer or a ground layer. There are various specific structures for the interconnection, and these are selected based, for example, on the particular support structure, the number of wiring layers, and the number of the wiring layers connected by the specific via.
Good radio frequency (RF) performance depends on the ability to transfer power between the various layers of the substrate without introducing excessive, additional RF loss. Previously, the RF ground vias in coplanar waveguide to three-wire to coplanar waveguide transitions have been connected to a ground layer and to the backside conductor. From an electromagnetics viewpoint, this type of geometry creates an unbalanced structure, which results in narrow band performance.
Multilayer interconnect manufacturers have not substantially addressed the problem of narrow band performance. This has made it apparent that a new technique for connecting multilayer components is needed. The new technique should substantially minimize electromagnetic field disturbance in multilayer interconnects. The present invention is directed to this end.
It is, therefore, an object of this invention to provide an improved and reliable multilayer radio frequency interconnect system. Another object of the invention is to substantially minimize electromagnetic field disturbance in multilayer interconnects.
In accordance with the objects of this invention, a multilayer radio frequency interconnect system is provided. In one embodiment of the invention, a multilayer radio frequency interconnect apparatus includes a plurality of laminated printed wiring boards made of a dielectric material with low loss characteristics for radio frequency electromagnetic radiation. In operation, a RF signal launches from a first signal conductor 24. A vertical transition from the first signal conductor 24 to a second signal conductor 44 is realized by a 3-wire transmission line. The center conductor of the 3-wire transmission line is a RF via 30. The two outer conductors are RF ground vias 32 and connect the first RF ground conductor 22 to the second RF ground conductor 42. These two RF ground vias 32 are isolated from the ground planes 40, 46 which are located between RF signal layers 20, 38. The advantage of this ground isolation is to maintain the 3-wire transmission line characteristic impedance and to reduce disturbance to electromagnetic fields such that a broadband design may be achieved. The RF ground vias are terminated at signal layers 20, 38.
The present invention thus achieves an improved multilayer radio frequency interconnect system. The present invention is advantageous in that it is capable substantially minimizing electromagnetic field disturbance in multilayer interconnects.
Additional advantages and features of the present invention will become apparent from the description that follows and may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims taken in conjunction with the accompanying drawings.